A. Field of the Invention
The invention relates to the field of pick and place machines such as are used to place components on a printed circuit board (xe2x80x9cPCBxe2x80x9d) in a manufacturing context. The invention relates more particularly to increasing the number of components that can be picked and placed in one placement cycle.
B. Related Art
Currently there are several types of component placement machines. Some have a single placement head and some have several placement heads. The placement heads may be disposed in a turret configuration or in a line, also called a xe2x80x9cbeamxe2x80x9d. The turret configuration typically includes multiple heads arranged around a circle.
The Philips Topaz is an existing component placement machine that has eight placement heads arranged in a beam. The placement heads are 16 mm apart. Each placement head includes a nozzle for holding a component in place by suction.
The standard Topaz can bring eight small parts from the pick to the place area in one pick and place cycle, by allowing a xe2x80x9cpay loadxe2x80x9d of eight parts per beam. For the purposes of this application, a xe2x80x9clargexe2x80x9d part is one which has at least one horizontal dimension greater than 12 mm. When large parts have to be turned in order to be placed, or when large parts exceed 12 mm in all horizontal dimensions, a problem arises. Namely two such parts cannot be placed on adjacent nozzles without a collision occurring between the parts.
Parts which are larger than 12 mm include DRAM chips commonly used for SIMM (Single In-line Memory Modules) boards. Such chips are commonly 18-22 mm in their larger horizontal dimension. FIG. 1 shows a typical arrangement of DRAM chips as they come from their manufacturer. The chips 102 come arranged like chocolates in a tray 103. Their first pin 101 has a known orientation in the tray, with all chips arranged in the same orientation.
The SIMM board 201, on which the DRAM chips are to be placed, is commonly oblong, as shown in FIG. 2. Depending on the layout envisioned by the board designer, the chips 102 may have any orientation when placed. For instance, a chip might be rotated by 90 degrees as shown at 202 or by 270 degrees as shown at 203. The pins 101 are shown with their different positions depending on the placement of their respective chips on the board.
When such larger parts are to be placed, the PCB manufacturer currently only uses alternate heads on a beam configuration machine to allow for the rotation required by a layout such as shown on FIG. 2. FIG. 3 shows a prior art beam configured pick and place machine 301 with 8 nozzles 302, like the Philips Topaz. When carrying the larger chips 102, half of the nozzles are empty. When only alternate heads are used, an eight head beam machine becomes no more effective than a four-headed machine. The enhanced component placement speed normally expected from having eight heads instead of four heads is lost.
However, spacing the eight heads farther from each other is not a viable option, because then component placement efficiencies would be lost for smaller components and a much larger and costlier frame design would be needed to allow all heads to reach all component pick-up locations.
The object of the invention is to create a beam configuration pick and place machine which is suitable for placing both large and small electronic components and also can carry larger components on all of its placement heads simultaneously.
This object is achieved by using nozzles of differing lengths in the beam configuration pick and place machine.